[Camino-users] anomalous high FA values

[Philip A Cook]

Hi Ian,

If the nonlinear fit fails to converge, you should get the linear result in the voxel. It sounds like it is converging (exit code 0) but it is converging on a bad solution. I expect that the ADC will be strange as well.

You might have better luck with RESTORE. 


Phil

On Jan 28, 2013, at 1:30 PM, Ian Malone wrote:

> Hi,
> 
> We're using Camino on some Siemens data, 42 directions, b=1000 s/mm^2, there are a few different protocols (different sites), but the problem seems to affect a few of them, one has 7 b=0 acquisitions. Fitting tensors using the non-linear least squares fit from modelfit we find a small number of voxels with FA>0.999, mostly in the caudate (sorry, don't have all the details yet on frequency). There are no obvious problems with the raw data and using FSL's FDT to do a simple least squares log signal fit doesn't produce this error. Looking at the error codes there are some 6's (bad data), but not corresponding to the problem voxels. I'd thought it might be a convergence problem, but we don't seem to be getting any error code = 2.
> 
> Does anyone have any suggestions for things we could try to solve this problem? The Camino version is a fairly recent release (r1014).
> 
> Thanks for your time,
> Ian
> 
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